Wear behavior of TiAlN coated WC tool during micro end milling of Ti-6Al-4V and analysis of surface roughness

Abstract

The demand for high quality micro components has been on the upsurge for the past few decades. Nowadays micro end milling is preferred to produce 3D micro parts. This paper presents an investigation on wear behavior of solid tungsten carbide (WC) tool with TiAlN coating during micro end milling of Ti-6Al-4V. Miniaturization of the tool combined with machining of hard to machine material like Ti-6Al-4V results in rapid tool wear. Feed/tooth to tool edge radius ratio (f/r) has got significant influence on micro end milling machining mechanism. For f/r less than one, ploughing is dominant, and the shearing mechanism prevails when f/r is greater than one. Therefore, experiments were carried out at two feed rates 0.3 µm/tooth and 5 µm/tooth to examine the effect of tool edge radius on tool wear. Tool wear in terms of flank wear, adhesive wear, abrasive wear, enlargement of tool edge radius, and delamination of coating was studied, and an investigation on the effect of tool wear on surface roughness was also carried out. A 3D optical profilometer was used to characterize tool wear and surface finish of the machined feature. With 0.3 µm/tooth feed rate, tool fails after ~700 mm length of cut and with 5 µm/tooth feed rate, tool fails after ~1000 mm length of cut. For both 0.3 µm/tooth and 5 µm/tooth feed rates tool fail approximately at 15–20 µm flank wear width. Adhesive wear was found to be the major tool failure mechanism for both feed rates. Moreover, in micro end milling operation selecting a feed rate slightly above the tool cutting edge radius will be beneficial so that a good surface finish is obtained during initial stages of the wear.